1. Field of the Invention
This invention relates to the field of audio signal processing circuitry, and, more particularly, to a circuit for mixing signals from audio sources that provides noise reduction.
2. Description of the Related Art
It is often desirable to mix audio signals from several different sources in order to produce a combined audio signal. In some situations, a source signal containing a relatively high level of noise may be combined with a source signal containing a relatively low level of noise. Such a combination of audio signals, when implemented according to known techniques, often results in relatively high noise levels at the output.
A typical situation is a combination of signals from a compact disc player, which has relatively low noise, with signals from a personal computer, which has relatively high noise. Such signals may be combined so that the computer can issue an "alert" sound, such as a beep, at a particular time while a user is listening to a compact disc. According to conventional signal combination techniques, the high levels of noise from the personal computer will be present in the combined signal, and may therefore be distracting or offensive to the user when he or she is listening to the compact disc.